1. Field of the Invention
The present invention relates to a camera, and more specifically, to a camera using films each including a development processing solution.
2. Related Art Statement
A camera using films each including a development processing solution has been conventionally well known as a so-called instant camera by which a photograph can be observed at once at the place it was taken.
The instant camera generally uses a sheet-shaped instant film, and a film called a mono-sheet type film included in the sheet-shaped instant film need not be separated to two sheets after being photographed and thus can be easily handled.
Various types of cameras using the mono-sheet type film have been conventionally proposed and, for example, Japanese Patent Publication Laid-Open No. 1-298335 discloses an example of these cameras.
The film and camera disclosed in the publication will be described with reference to FIG. 1.
The mono-sheet type film denoted by numeral 7 in FIG. 1 has an exposing portion 19 which is formed to a size a little smaller than the periphery of the film 7 and the surface of the exposing portion 19 is covered with transparent plastics where the image of a subject is exposed.
A processing solution accommodating bag 8 accommodating a development processing solution is disposed along an edge of the film 7. In the following description, the side of the film 7 where the processing solution accommodating bag 8 is provided is described as a front edge and the other side of the film 7 opposite to the front edge is described as a rear edge. Note, the portion between the processing solution accommodating bag 8 and the exposing portion 19 is initially sealed.
The camera is provided with an electromagnetic motor 90 as an actuator and the rotational force of the electromagnetic motor 90 is transmitted to an upper roller 92 disposed on the upper side of the film 7 to be fed and to a lower roller 93 disposed on the lower side of the film 7 through a gear train 91 including a reduction gear.
Note, since the electromagnetic motor 90 is a type of a motor which generates torque when it rotates at a high speed, the reduction gear is an indispensable element.
The upper roller 92 and the lower roller 93 are rotated in the directions of arrows 92a and 93a by the gear train 91, respectively to feed the film 7 in the direction of an arrow 7a.
A rotary shaft 92d for transmitting a rotational force from the gear train 91 is integrally connected to an end of the upper roller 92 and a rotary shaft 92e coaxial with the rotary shaft 92d is integrally connected to the other end of the upper roller 92. These rotary shafts 92d, 92e are rotatably supported by bearings 92b, 92c, respectively.
A rotary shaft 93d for transmitting the rotational force from the gear train 91 is integrally connected to an end of the lower roller 93 and a rotary shaft 93e coaxial with the rotary shaft 93d is integrally connected to the other end of the lower roller 93. These rotary shafts 93d and 93e are rotatably supported by bearings 93b, 93c, respectively.
A spring 94 is interposed between the bearing 92b and the bearing 93b and a spring 95 is interposed between the bearing 92c and the bearing 93c, respectively.
These springs 93, 94 are used to keep certain distances between the bearings 92b, 93b and between the bearings 92c, 93c when no external force is applied therebetween, whereas when external forces are applied in a direction to increase the distances therebetween, the bearings 93, 94 generate contraction forces in the direction opposite to the external forces. That is, the bearings 92b and 92c are attracted in the directions of arrows 96, 98 and the bearings 93b and 93c are attracted in the directions of arrows 97, 99.
With this arrangement, when the external force is not applied between the upper roller 92 and the lower roller 93, that is, when the film 7 is not yet held between the rollers 92 and 93, the interval between the rollers 92, 93 are kept to a certain value.
When the external force is applied between the upper roller 92 and the lower roller 93, that is, when the film 7 is held between the rollers 92 and 93, a press force is applied to the film 7 therebetween by the contraction forces of the springs 94, 95. FIG. 1 shows the state that the portion of the processing solution accommodating bag 8 along the front edge of the film 7 is held between the upper roller 92 and the lower roller 93 and the press force is applied thereto.
The film 7 having been exposed by the camera arranged as described above will be processed as described below.
After the image of a subject is exposed to the exposing portion 19 of the film 7, the processing solution accommodating bag 8 along the front edge of the photographed film 7 is fed while being pressed by the two rollers 92, 93, so that the seal of the processing solution accommodating bag 8 is broken. Then, the development processing solution accommodated in the processing solution accommodating bag 8 is spread on the side of the exposing portion 19.
At the time, since the surface of the developing portion 19 is covered with the transparent plastics as described above, even if the development processing solution is spread, it does not leak to the outside.
When the press force is continuously applied toward the rear edge of the film 7 by the rollers 92, 93, the development processing solution is spread over the entire surface of the exposing portion 19 and a development processing is carried out. At the time, the development processing solution must be uniformly spread over the entire surface of the developing portion 19 to carry out the development processing without irregularity.
At the same time, the film 7 is discharged to the outside of the camera by the rotation of the two rollers 92, 93. Otherwise, when a photographed film accommodating chamber is provided with the camera, the film 7 is fed into the chamber. Then, after a predetermined period of time elapses, the image of the subject is formed on the exposing portion 19 and thereafter the development is automatically stopped.
In the camera disclosed in Japanese Patent Publication Laid-Open No. 1-298335 as described above and the like, since the upper and lower rollers must be rotated while they apply a press force to a film, a large amount of energy is lost in the bearings of the rollers and thus a strong motor is required.
Since the electromagnetic motor is used as the actuator of a processing solution spread unit, the reduction gear is required and a problem arises in that the structure of the camera is made complex by the reduction gear, large operation sound is produced and electromagnetic noise may be generated.
In order to uniformly spread the development processing solution, a high dimensional accuracy is required to the rollers to finish the surfaces thereof uniform, by which a cost is increased.
Since the film must be fed straight in a predetermined direction to uniformly spread the development processing solution, guides are required on the both sides of the film.
Incidentally, since an instant film is developed at a place where it was photographed, the temperature of a development processing solution is approximately equal to the environmental temperature of the camera. As a result, when a photograph is taken at, for example, a cold place, there is a problem that the temperature of the development processing solution also becomes low and development slowly progresses.
To cope with the above problem, the applicant proposes a device disclosed in Japanese Patent Application No. 5-297059 as an example of conventional devices. This proposal is arranged such that a development processing solution contained in a film is heated through rollers pressed against the film when the film is fed.
More specifically, a heater is provided to heat the roller as well as a temperature sensor is disposed to a bearing of the roller and the temperature of the roller is controlled with reference to an output from the temperature sensor.
However, the device disclosed in Japanese Patent Application No. 5-297059 must provide the heater as dedicated roller heating means, by which the structure of the device is made complex.
Further, since the roller rotates, the temperature sensor cannot be directly fixed on the roller and is inevitably disposed to the bearing of the roller. Thus, it is difficult to correctly detect the temperature of the roller. In addition, the environmental temperature of the camera is not measured, a heat control cannot properly be carried out in accordance with the environmental temperature.